Or to be exact, 40 hours and 40 minutes of 100% renewables generation between 1 am on February 14 and 17.40 on February 15. But still enough to eclipse the 33 hours of 100% renewables generation achieved at King Island, Tasmania, last November. So congratulations to the GdV project staff.
Here are the REE ten-minute generation values for the EL Hierro grid over the period of interest:
Except for a small amount of hydro generation when wind generation dropped off in the early afternoon of February 14 El Hierro’s electricity demand was filled entirely by wind. (Wind speeds at El Hierro airport 3 km to the northeast ranged from 8 to 13 m/s over the period). This is in contrast to the 16 hours of 100% renewables generation achieved on January 16, when the wind abruptly died and the test continued with a mixture of wind and hydro (see Figure below). Otherwise the only operational change since the January seems to have been that wind was curtailed at around 7MW rather than around 6MW:
My preliminary questions are (others may occur to me later):
1. Why was the test terminated at 17.40 on February 15? Except for a tiny amount of hydro generation when the wind briefly fell off at 17.10 (barely visible on the first plot) there was no significant change in the generation mix, and 41 hours and 40 minutes is hardly a nice round number.
2. Grid stability during the test was probably maintained by using pumping as a dynamic resistor to soak up excess wind and by spinning three of the 2.83 MW hydro turbines to achieve the necessary system inertia. But if it’s that simple, why don’t they do it all the time?